This project represents a continual effort to quantify the key biomechanical characteristics of human laryngeal tissues, so as to better understand the tissue mechanics of voice production, the potential mechanical factors responsible for voice disorders related to vocal overuse and trauma, and the mechanical manifestations of vocal fold scarring. The long-term goal is to provide mechanics-motivated guidelines for improving the prevention, diagnosis and management of voice disorders. To achieve this goal, the specific aims of this application include: (1) To quantify the linear and nonlinear viscoelastic response of the vocal fold lamina propria extracellular matrix (ECM), including to quantify the tissue fatigue response contributing to the safety limits of accumulated vibration exposure in the vocal fold ECM, and to quantify the viscoelastic shear properties of human vocal fold scar tissues; (2) To characterize the active contractile properties and passive viscoelastic properties of human intrinsic laryngeal muscles; (3) To develop new constitutive models of the vocal fold lamina propria and the intrinsic laryngeal muscles for more accurate descriptions of their tissue mechanics; and (4) To develop new biomechanical models for fundamental frequency regulation and prediction; as well as to integrate the new empirical data and new constitutive models with existing computational biomechanical models of vocal fold posturing and phonation. A major benefit of this research will be an improvement in the computer models of vocal fold posturing and phonation, such that they will become more accurate, more consistent and more representative of human voice production. Such models can potentially become a powerful clinical tool for maximizing the vocal function of patients undergoing phonosurgical procedures, such as thyroplasty, injection laryngoplasty and minithyrotomy for the treatment of a variety of voice disorders. PUBLIC HEALTH RELEVANCE: Up to 9% of Americans suffer from some kind of voice disorders annually. The economic impact of voice disorders cannot be overstated, as up to around 20% of the U.S. workforce relies on a healthy, functional voice as a major tool for their occupations (Titze et al., 1997). It has also been well documented that voice disorders have a significant negative impact on the quality of life in the areas of communication, social function and psychological health. By improving our understanding of the tissue mechanics of voice production, the potential mechanical factors responsible for voice disorders related to vocal overuse and trauma, and the mechanical manifestations of vocal fold scarring, this research may contribute findings that could improve the prevention, diagnosis and management of voice disorders, reducing the burden of excessive healthcare costs on society.